The present invention relates to an actuation and control device for opening/closing switchgear, particularly circuit breakers for high- and medium-voltage transmission and/or distribution networks. The device according to the invention is now described with reference to a high-voltage circuit breaker without intending in any way to limit the scope of its application.
An example of a single pole of a high-voltage circuit breaker provided with a known type of actuation device is shown schematically in FIG. 1. A first post-shaped supporting insulator 2 is arranged on a supporting frame 1 and a second insulator 3 is arranged on the upper end of said first insulator; an interruption chamber is provided inside said second insulator and has circuit breaking mechanisms which comprise fixed contacts and moving contacts. Opening/closure is performed by engaging/disengaging the fixed contacts with respect to the moving contacts. The moving contacts are operatively connected to an actuation rod which runs, inside the supporting insulator 2, from the moving contacts to the base of the post. The rod is actuated by means of kinematic systems which are located in a housing 4 at the base of the post and are operatively connected to an actuation device 5. Actuation devices for high-voltage circuit breakers are currently of the mechanical or hydraulic type.
The mechanical actuation device generally uses two springs, namely a closure spring and an opening spring, a stroke limit damping system, a reloading motor for the closure spring and a mechanism which allows to convert the motion produced by the springs into a translatory motion of the moving contact, to reload the opening spring and to make the opening movement independent of the closure movement.
According to a known embodiment, the mechanical actuation is provided by means of the device shown in FIG. 2, in which the following elements can be identified: an opening spring 10, an opening device 11 actuated by an electromagnet, an eccentric element with a lever 12, a closure device 13 actuated by an electromagnet, a main shaft 14, an arm 15 rigidly coupled to the shaft 14, a closure spring 16, a damping unit 17, a drum 18 and a gearmotor 19.
Another example of known mechanical actuation device is described in U.S. Pat. No. 5,151,567 and is shown schematically in FIG. 3. In this case, the movement of the main shaft 20 during the opening of the circuit breaker (in the direction of the arrow 28 of FIG. 3) is produced by virtue of the action of a spring 21 which is conveniently positioned and connected to the main shaft 20 by means of the crank 22. The movement of said rod is allowed by a release mechanism 23. During closure (direction of the arrow 27 of FIG. 3), the main shaft 20 is moved by means of a motor 24 which is directly coupled to the main shaft 20 and is actuated by an electronic unit 25 supplied by the power supply block 26. The action of said motor also allows to reload the opening spring 21. Accordingly, the closure spring is eliminated and the spring 21 is used only during opening, the opening speed being preset by selecting the dimensions of the spring.
However, in the above solution there is no active control of the position and motion of the actuation shaft 20 during the opening and closure of the circuit breaker.
Many other configurations are available as an alternative to the illustrated ones, but the mechanical actuation devices of the known art generally have a large number of components which require a long and complicated initial calibration. Despite performing the task to which they are dedicated, these devices have several drawbacks in addition to their already-mentioned mechanical complexity. The movement of the moving contact is in fact determined exclusively by the elastic characteristic of the opening and closure springs: the rule of motion of the moving contact cannot be changed by the user but is set during design. Actuation devices of the hydraulic type, in which the movement of the moving contact is ensured by suitable hydraulic actuators, can partially obviate these drawbacks, but they have disadvantages linked to the presence of fluids, especially owing to their temperature-sensitivity.
The use of springs and the lack of control over the rule of motion of the actuator furthermore require the presence of damping elements or shock-absorbers in order to dissipate the residual kinetic energy at the end of the movement and to avoid uncontrolled impacts against the pole. Moreover, precision in the positioning of the moving contact is limited by a mechanism which is inherently inaccurate owing to the presence of the springs.
The energy that must be supplied is furthermore greater than the energy strictly necessary to move the moving contact, since it is also necessary to move the various mechanical elements of the actuation device.
The aim of the present invention is to provide an actuation and control device for high- and medium-voltage circuit breakers (i.e. for voltages greater than 1000 V) which allows to move the moving contact of said circuit breaker according to a predetermined rule of motion.
Within the scope of this aim, an object of the present invention is to provide an actuation and control device for high- and medium-voltage circuit breakers whose mechanical complexity is reduced.
Another object of the present invention is to provide an actuation and control device for high- and medium-voltage circuit breakers which allows to preset the positioning precision of the moving contact both during opening and during closure.
Another object of the present invention is to provide an actuation and control device for high- and medium-voltage circuit breakers which ensures repeatability of the movement, optionally compensating variations due to aging and wear.
Another object of the present invention is to provide an actuation and control device for components of high- and medium-voltage circuit breakers which has reduced response times.
Another object of the present invention is to provide an actuation and control device for components of high- and medium-voltage circuit breakers which is highly reliable, relatively easy to manufacture and at competitive costs.
Thus, the present invention relates to an actuation and control device for opening and closing high- and medium-voltage circuit breakers having at least one fixed contact and at least one moving contact, said device comprising actuation means which are operatively connected to the moving contact and supply the energy for performing the opening/closure movement. The device according to the present invention is characterised in that said actuation means comprise a servomotor, an electronic control and power supply unit for driving said motor, and elements for transmitting motion between the motor and the moving contact, and it is further characterised in that said actuation means and/or the coupling between the fixed contact and the moving contact are such as to achieve a desired speed of the moving contact at the instant in which it separates from the fixed contact during the opening movement.
The device according to the invention, in addition to ensuring a desired speed of the moving contact at the instant in which the contacts separate, is furthermore capable of controlling the rule of motion during the entire opening and/or closure movement.
Control of the speed of the moving contact at the instant in which it separates from the fixed contact allows to optimize the quenching times of the electric arc between the contacts.
Control of the rule of motion of the moving contact allows to ensure the accuracy and repeatability of the movement. The actuation device is furthermore highly simplified with respect to known types of actuation system, since it allows to eliminate springs of the spiral or other type, the motor for reloading the closure spring, and all the mechanisms that allow to perform the movement cycle; accordingly, the space occupation is also reduced. Furthermore, as a consequence of constructive simplicity, the need for maintenance interventions is reduced.
The elements for transmitting motion between the motor and the moving contact and the coupling between the moving contact and the fixed contact furthermore ensure the movement of said moving contact at a desired speed without this entailing an oversizing of the servomotor. The term servomotor is generally used to define motors having a feedback control system.